The present invention relates to a surface light source device in which a frame is arranged along the peripheral portion of a light emitting face of a light source section, such as a liquid crystal display device including a backlight section as a light source section at a back face of a liquid crystal display panel, and particularly relates to improvement in the frame thereof.
In general, in a liquid crystal display device including a backlight section at the back face of a liquid crystal display panel, the liquid crystal display panel is mounted at a frame of the backlight section and a bezel (rim) is arranged on the peripheral portion of the liquid crystal display panel for reinforcing the liquid crystal display panel mounted and for protecting the peripheral portion of the liquid crystal display panel.
Meanwhile, upsizing of liquid crystal display devices used in liquid crystal television sets is recently being promoted. In association therewith, higher strength is demanded. While, the rim portion of the bezel is required to be narrowed. Therefore, it is difficult to increase the strength by widening the rim portion of the bezel.
To tackling this problem, Japanese Patent Application Laid Open Publication No. 2000-75273A discloses that the strength of the casing is increased without inviting increase in thickness thereof, which shall accompany widening of the peripheral portion of the bezel, by arranging a flame of an L shape in section having an opening at a part corresponding to a display region of a liquid crystal display panel between a back frame of a backlight section and the liquid crystal display panel.
Also, Japanese Patent Application Laid Open Publication No. 2003-50549A discloses that such a frame is composed of a plurality of divisional members obtained in such a manner that the members is cut out from a metal plate, bent into an L shape, and then, connected with each other by using a L-shaped metal fitting so that waste part of the metal plate is lessened and the strength of the frame is increased though the frame is composed of the plural divisional members, compared with the case where the frame is merely cut out from a metal plate.
Moreover, Japanese Patent Application Laid Open Publication No. 2001-249619A discloses that in the case where a frame of an L shape in section used in a liquid crystal display device is composed of a plurality of divisional members, each connected end portions of the plural divisional members of the frame are welded in the side face portion of the frame.
However, in the above conventional cases, small slits are liable to be formed at the connected portions between the divisional members in the front face portion of the frame, and light of the light source section leaks through the slits.